In development history of a wireless local area network (WLAN) protocol, there is no perfect formal specification for application of an orthogonal frequency division multiple access (OFDMA) technology and an uplink multiple user multiple-input multiple-output (MU-MIMO) technology in an existing WLAN protocol. Thus, some new technologies may be introduced in a next generation WLAN protocol, such as the OFDMA technology and the MU-MIMO technology, thereby exploiting performance advantages brought by these new technologies in the next generation WLAN system. The next generation WLAN system and the existing WLAN system have a shared spectrum. Thus, how to ensure compatibility between the next generation WLAN system and the existing WLAN system is a question.
In an IEEE802.11 protocol of the existing WLAN system, a media access control (MAC) layer uses a carrier sense multiple access with collision avoidance (CSMA/CA) protocol to ensure backward compatibility. In the IEEE802.11g protocol of the WLAN system, a Clear To Send-to-self (CTS-to-self) mechanism and a Request To Send/Clear To Send (RTS/CTS) mechanism are used to ensure backward compatibility during data transmission and to avoid a conflict between channels. The CTS-to-self mechanism is a mechanism over a MAC layer, which is used to protect a frame sequence from interferences of an adjacent station at an initiating end. In a CTS-to-self mode, when preparing to use a channel, a station in a protocol transmits a CTS frame firstly, where a receiving address of the frame is set to its own MAC address, a duration field thereof is set to its own MAC address, and the “duration” field is set to the difference of an estimated sequence time length and a time length of the CTS frame itself, which indicates how much time a station currently using a physical medium will take a wireless link subsequently. The CTS frame is transmitted at a basic rate, which is compatible with a conventional 802.11b station and can be identified by all stations in the network; other stations that sense the CTS frame update their own network allocation vector (NAV) values based on this, and remain silent during this period of time. The RTS/CTS mechanism is another alternative protection mechanism, which is used to protect a frame sequence from interferences of an adjacent station at an initiating end and a receiving end. The initiating end transmits an RTS frame, and the receiving end replies with a CTS frame after receiving the RTS frame. Relatively speaking, when the RTS/CTS mechanism is used, two additional control frames need to be exchanged before each data transmission is performed. However, both of the transmission mechanisms allow only one station to access and transmit data during data transmission at one time. Thus, new efficient technologies such as the OFDMA and the UL MU-MIMO introduced in the next generation WLAN protocol cannot be used, which is unfavorable for improvement of network performance.